The purpose of this multi-disciplinary project is to provide this outstanding candidate with mentored training in patient-oriented research focused on complications of cirrhosis and liver transplantation (LT) outcomes and to prepare her for a career as an independent clinician-scientist. The candidate's research and training activities will be closely supervised and guided by a primary mentor, co-mentors, an Advisory Committee and consultants, each with unique expertise germane to different aspects of the proposed project. The candidate's preliminary data showed that women with serum creatinine (Cr) e 1.0 mg/dl had lower survival rates on the LT waiting list compared to men; this was likely caused by underestimating renal dysfunction in women when using Cr rather than glomerular filtration rate (GFR) to calculate Model for End-Stage Liver Disease (MELD) scores. Moreover, serum Cr is not an accurate biomarker to detect kidney dysfunction in cirrhosis regardless of gender. The PI will test the hypotheses that (1) gender disparity is caused by underestimating severity of kidney disease in women when using serum Cr rather than GFR to calculate MELD scores, (2) that cystatin C and symmetric dimethylarginine (SDMA) are more accurate biomarkers of renal function in cirrhosis than Cr, and (3) that an equation that includes serum cystatin C, SDMA or both and patient characteristics will be more accurate and precise for determining renal dysfunction in subjects with cirrhosis than existing Cr- and cystatin C-based GFR-estimating equations that were derived in populations without cirrhosis. To test these hypotheses, the PI proposes three Specific Aims: 1) Test the hypothesis that gender disparity on the LT waiting list is caused by underestimating renal dysfunction in women when using serum Cr rather than GFR to calculate MELD scores. The PI will elucidate factors underlying gender disparity on the LT waiting list by analyzing United Network for Organ Sharing data of subjects with cirrhosis listed between 2002 and 2009. 2) Establish an accurate biomarker of kidney function in cirrhosis. The PI will enroll 100 subjects with cirrhosis, directly measure GFR using the validated method of non-radiolabeled iothalamate plasma clearance and simultaneously measure serum cystatin C, SDMA, Cr and 24-hour urinary Cr clearance and compare the accuracy of each biomarker for estimating true GFR. 3) Develop an accurate and precise equation to estimate GFR in cirrhosis. The PI will derive and assess the performance of a novel GFR-estimating equation in cirrhosis, based on serum cystatin C, SDMA or both and patient characteristics. The results of this study are anticipated to spur modifications of the MELD score that will reduce gender disparity in liver allocation and establish an inexpensive, readily available, accurate, non-invasive measure of kidney function in cirrhosis. The mentored research training and courses supported by this K23 award will provide the PI with excellent grounding for a successful academic career in health services and patient-oriented research.